


Wipe The Blood And Wash Away The Dust

by Its_Raining_Here



Series: Yandere!Sans [1]
Category: Undertale (Video Game)
Genre: Abuse, Child Abuse, Child Neglect, Creepy Sans (Undertale), Good Intentions, M/M, Murder, Overprotective Sans (Undertale), Sans is one creepy lil dude, Yandere, Yandere Classic Sans, Yandere Sans (Undertale), Young Papyrus (Undertale), Young Sans (Undertale), i think, their mom sucks
Language: English
Status: Completed
Published: 2021-01-20
Updated: 2021-01-20
Packaged: 2021-03-12 05:28:58
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 1
Words: 1,385
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28880250
Author URL: https://archiveofourown.org/users/Its_Raining_Here/pseuds/Its_Raining_Here
Summary: Sans and Papyrus' mom isn't the best. She plays favorites, always neglecting Papyrus and trying to pamper Sans.Sans doesn't like that.One day, she goes too far, and pays the price.
Relationships: Papyrus/Sans (Undertale)
Series: Yandere!Sans [1]
Series URL: https://archiveofourown.org/series/2117982
Comments: 8
Kudos: 52





	Wipe The Blood And Wash Away The Dust

**Author's Note:**

> ive written SO MUCH Yandere!Papyrus, but ive never written Yandere!Sans
> 
> i always see it done with swap sans, but i really like classic, so i wrote this
> 
> enjoy!

From the moment Papyrus was born, Sans swore to protect him with his life.

He hadn’t expected the first thing he’d protect his precious brother from to be their own mother.

Sans was only 12 when it happened.

Papyrus was just 5 years old.

Their mother was in the kitchen cooking dinner, humming along to the song on the radio.

Papyrus and Sans were sitting in the living room, playing with their action figures.

“And then! Then the sci...sss…” He trailed off.

“scientist.” Sans finished for him.

“Yes, thank you Sans! Then the scientist found the cure for the evil sickness, and everyone was happy!” Papyrus shouted, his voice full of childlike joy.

“that was a great story pap! it was really creative.” Sans smiled at his baby brother.

“Really? You really think so Sansy?!” Papyrus gazed up at him with a wide smile on his face. Sans’ soul fluttered whenever Papyrus called him by that nickname.

“i sure do! no ones a better storyteller than the great papyrus!” Sans stood up, and scooped his brother into his arms.

“Nyeh heh heh! Spin me around Sansy! Please?” 

“alright, hold on tight.”

Sans lifted Papyrus into the air, and spun around quickly, making sure he had a tight grip on his younger brother.

Papyrus giggled and squealed happily as Sans spun him through the air, ending off with falling onto the couch.

“Again! Again!” Papyrus climbed on top of Sans, and tried to pull him up.

“nah bro.” Sans panted, out of breath, “m’too tired.”

“No, you’re just lazy! C’mon, Sansy! Pretty please?”

“Keep it down in there! You’re giving me a headache.” Their mother called from the kitchen.

Sans scowled. That woman always seemed to have a headache, she only ever said it when Papyrus was playing.

“Sorry mama!” Papyrus apologized.

His precious baby brother shouldn’t have to apologize to her. She’s always yelling at him for minor offences, like leaving the crayons out, or forgetting to turn off a light. Why is it always his fault?

They sat on the couch and talked for about 10 more minutes, when their mother called them to eat dinner. 

Before Sans could stop him, Papyrus jumped up from his spot, and sprinted over to the kitchen at full speed. He tried to turn the corner, but slipped and fell face first, landing right onto a cabinet.

Time seemed to slow down, as their mother’s favorite flower vase wobbled, and fell onto the floor with a loud _crack!_

Sans ran over from the couch to his brother, who was holding his hands up to his head, face scrunched up as if in pain.

“oh stars, paps, are you okay!?” Sans checked over Papyrus for any other injuries.

“What in the angel's name-!” Their mother stomped into the living room, and her eye lights landed on the now broken shards of glass.

She walked over to where Papyrus and Sans were, and didn’t even look at them before she gathered a handful of the pieces.

“Papyrus...what did you do?! This was from your grandmother!” She glared at him, “How could you be so careless? We can’t replace this!”

“I-I’m sorry mama! I didn’t mean t-to!” Papyrus cried.

Sans hated it when their mother yelled. She complained about Papyrus being too loud, but screamed like a banshee when she was upset.

Their mother swiftly walked over the Papyrus, and slapped him across the face. He fell over from the force of it.

.  
.  
.

I’m sorry, _what?_

She did _not_ just do that.

“You need to learn not to run in the house! How many times have I told you?” She scolded.

“I’m sorry! It was an accident mama!”

“Don’t give me that bullshit! Why are you so destructive?” She kicked him in the ribs, “Go to your room!”

Papyrus quickly got up and ran to their shared bedroom, quietly closing the door behind him. Sans was left staring at the door. Their mother turned to him, and softened her glare.

“I’m sorry you had to be involved in that sweetie. He’ll learn to calm down eventually.” She turned and walked back into the kitchen after cleaning up the vase shards.

Mother always favored Sans. He was quiet, got good grades, and was well behaved in school and at home. Sans didn’t understand why she disliked Papyrus. He never did anything wrong, he was just being a kid. Sans was sure he’d been just as hyperactive when he was younger.

How could she hit Papyrus? Adorable, kind, sweet Papyrus? How could she? How _dare_ she?

She would need to pay for what she’d done.

Sans was quiet all through dinner, only speaking when his ‘mother’ asked him a question. When he did answer, his words were short and to the point. He didn’t want to speak to her more than he had to.

She didn’t seem to notice his off attitude. 

Good.

When dinner was finished, Sans took another plate without his mother noticing, and brought it up to his room, where Papyrus was laying down on his bed, pretending to be asleep.

“hey bro. got you some food.” He said softly, placing the plate on the nightstand.

Papyrus lifted his head and looked at him, “Not hungry…” He pulled the blanket over his head.

Sans sighed, “c’mon paps. you gotta eat your dinner if you want to join the royal guard.”

That made Papyrus sit up.

“Oh alright...thank you brother.” He ate dinner slowly, but at least he was eating.

“no prob.” Sans said calmly. Internally, he was fuming at the sight of that red mark on Papyrus’ face.

When Papyrus was done, Sans checked his soul.

_PAPYRUS_  
HP: 100/100  
Just wants to forget today. 

“well, your hp is full. that's a relief.” Sans patted Papyrus’ back, and sat down on the bed next to him.

Papyrus yawned, and cuddled up to Sans, closing his eye sockets.

Sans smiled, and stayed with him until he fell asleep, using a light healing spell to get rid of the bruises.

When Papyrus finally drifted off, Sans laid him down under his blanket, and quietly snuck out of their room. It was around 11 pm, so their mother was likely already in bed.

With the only sound being the creaking floorboards, and the ticking clock, Sans made his way over to the kitchen, and opened the utensil drawer.

Right within his reach, was a bright, shiny kitchen knife.

He picked it up, feeling the heavy weight of the metal.

Mother was going to pay for what she did to Papyrus.

No one will ever hurt Papyrus again.

Sans slowly walked to their mothers room, knife in hand, and a plan in mind.

He was going to kill her.

He was going to make her regret ever hurting Papyrus.

The door to her bedroom creaked open, and he stepped lightly, as to not make any noise. When he was standing over her sleeping form, he pressed his hand to her mouth to muffle her screams, and plunged the knife into her skull.

The bone cracked and splintered and fell apart on impact, breaking off with a loud _crack!_

Over, and over, and over, he stabbed her head. 

Blood splattered across the wall, and all over the bedsheets.

A thin layer of dust coated his hands, and the knife.

His mother was dead.

And he killed her.

He smiled.

\-----------------

“Sans, where’s mama?” Papyrus asked innocently.

“she’s gone away for a vacation. she won’t be back for a while, so you and me are going to go on our own vacation!” Sans smiled at his brother, holding his hand for the whole walk out of New Home.

“Ooooh! A vacation? Where are we going Sansy?” He smiled so bright, Sans considered buying sunglasses.

“we’re going to snowdin!”

Papyrus gasped, “Oh my god! Can we build snowmen when we get there? Can we have a snowball fight?”

Sans giggled, “sure thing bro, we can do whatever you want.”

His brother squealed happily, and hugged him tightly.

“You’re the best big brother ever!”

\-----------------

Sans had made sure to clean up his mess, washing his now dead mother’s dust down the sink drain, wiping off all of the blood, and burning the bedsheets. 

He kept the knife, however.

After all…

Who knows when he’ll need it?

**Author's Note:**

> this was really fun, definitely gonna write more. if you have any requests, leave them down in the comments!
> 
> also, i formed a new headcanon while writing this. i was thinking, "wait why would sans use a knife when he has magic" AND THEN I THOUGHT   
> "woah wait what if physical weapons like swords and knives and guns hurt monsters more than magic attacks? since monsters are made of magic?" so he uses a knife to maximize damage.
> 
> hooray i think


End file.
